POWER-SUPPLY APPARATUS, DISCHARGE-LAMP LIGHTING APPARATUS AND ILLUMINATION APPARATUS

摘要

PURPOSE:To reduce the voltage applied to a switching device while the distortion of an input current is being made low and a high input power factor is being kept by a method wherein a current which flows to an inductance during one cycle of a switching operation is made discontinuous. CONSTITUTION:When a switching device Tr is turned on and off, a high-frequency AC voltage is generated across both ends of a resonant circuit which is connected to a drain for the switching device Tr. The high-frequency voltage is applied across an inductor L1 and a diode D2 via a capacitor C2. Thereby, the diode D2 repeats an ON-OFF operation at a frequency which is higher than the frequency of an input AC power supply Vac. As a result, an AC input current flows into in a part where the instantaneous voltage of an input AC voltage is low. That is to say, the input current flows in parts other than a part near the peak value of the AC voltage, it is distortion becomes low because an envelope is brought close to sine waves, and an input power factor can be increased.